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Diesel fuel injection systems are operating at increasingly higher pressure (up to 250 MPa) with smaller clearances, making them more sensitive to diesel fuel contaminants. Most liquid particle counters have difficulty detecting particles <4 μm in diameter and are unable to distinguish between solid and semi-solid materials. The low conductivity of diesel fuel limits the use of the Coulter counter. This raises the need for a new method to characterize small (<4 μm) fuel contaminants. We propose and evaluate an aerosolization method for characterizing solid particulate matter in diesel fuel that can detect particles as small as 0.5 μm. The particle sizing and concentration performance of the method were calibrated and validated by the use of seed particles added to filtered diesel fuel. A size dependent correction method was developed to account for the preferential atomization and subsequent aerosol conditioning processes to obtain the liquid-borne particle concentration.

The 2007 Diesel particulate matter (DPM) standard of 0.01 g/bhp-hr represents a 90% reduction of the previous standard and corresponds to roughly 100 micrograms (μg) gained on the filter sample used to determine compliance. The factors that influence the accuracy and precision by which this filter can be weighed are analyzed and quantified. The total uncertainty, representing best and typical cases, is between 1 and 5 μg. These uncertainties are used to compute the total uncertainty of the brake specific emission calculation. This uncertainty also depends on flowrate uncertainty, face velocity, and secondary dilution ratio. For a typical case, the total fractional uncertainty is in the range of ∼5 – 70% at 10% of the standard and ∼1 – 10% at 90% of the standard.

EPA's 2007 Diesel particulate matter (DPM) standard requires a large reduction in total mass emissions. In practice, this amounts to a fractional reduction in elemental carbon emissions. The reduction is balanced by a fractional increase in the semi-volatile component, which is difficult to sample and quantify accurately at low concentrations using filter-based methods. In this work, we show how five imprecisely defined filter-sampling parameters influence the mass collected on a filter. These parameters are: dilution air quality, dilution conditions (dilution ratio and dilution air temperature), particle size classification, filter media and artifacts, and face velocity. Each factor has the potential to change the mass collected by a minimum of 5% of the standard, suggesting there is room for improvement.

Many engine exhaust emissions measurements require exhaust dilution. With low-emission engines, there is the possibility for contaminants in the dilution air to contribute artifacts to the emissions measurement. The objectives of this work are to discuss common methods used to clean the dilution air, to present the detailed analysis of a pressure swing adsorption (PSA) system and to compare the performance of the PSA with 2 other systems commonly used to provide dilution air for engine exhaust nanoparticle measurements. The results of the comparison are discussed in context with some emissions measurements that require exhaust dilution.